The invention relates to an electromedical apparatus, in particular a current stimulation apparatus, comprising an output stage as current waveform generator for the output current to be produced through a patient's body as the load resistance, which generator operates with a specifiable operating voltage and controls the patient current in a constant-current fashion in the case of varying load resistance, and wherein the voltage drop is measured at defined resistance means in the operating voltage circuit for the purpose of determining the patient current; the magnitude as well as peak values of the patient current can be supplied to display units.
The utilization of constant-current stages in the case of stimulation current treatment has the advantage that patient resistances varying during the treatment, which could bring about a change in the current, are automatically controlled. However, on the other hand, the actually flowing patient current must be constantly monitored and displayed. In particular, in the case of utilization of pulse-shaped stimulation currents (for example, a triangular pulse waveform), specifically the peak values of the stimulation current pulses are also to be detectable.
Customarily, for the purpose of obtaining a current measurement which is as precise as possible, a resistance is connected in the patient current circuit at which the voltage drop can be measured and transmitted, as a current-proportional measuring signal, to a display apparatus. For the purpose of display, gas discharge tubes are, for example, employed. Up to the present time it has been disadvantageous that such measured vaue processing and display units have a separate operating voltage requirement which can be high in certain cases. If one proceeds from the assumption that the current stimulation apparatus of the type initially cited already operates with comparatively high operating voltages of several hundred volts, a corresponding increase in potential results due to the separate operating voltage requirement for the measuring and display apparatus connected with the operating voltage circuit. Similar considerations also apply accordingly to the active components employed in the measured value processing circuit, such as operational amplifiers, and the like. Although the absolute operating voltage requirement for this purpose is comparatively low, the demands for voltage stability are higher. In the case of a high basic (or fundamental) potential, which is variable within certain boundaries due to the constant-current control, this makes an additional circuit-technical outlay for the purpose of voltage stabilization necessary.